Ricin

Introduction
Ricin is a potent cytotoxi that is synthesized in the endosperm cells of maturing Riccinus seeds(1). Ricin belongs to a small multi gene family(2) that is composed of eight members. It is also important to mention that Ricin is classified as a type II heterodimeric Ribosome Inactivatiing protein(1).

Structure
Ricin is a heterodimer that consists of a 32,000 Dalton A chain glycoprotein linked by a disulfide bond to a 32,000 Dalton B chain glycoprotein(2). The A chain enzyme is a globular protein with extensive secondary structure and a predominate active site(2); where the B chain is a lectin(2) that binds to galactose-containing surface receptors(3).

Physiology
The mechanism deployed by Ricin to gain entry to a host cell uses the heterogenic properties given to the toxin. Firstly the toxin arranges itself in such a way where its B chain can easily interact with the host cells receptors, and once acknowledgement happens, the B chain can fascilitate transport of the A chain into the cytoplasm(2). This association between the A and B chain is essential for toxicity(2) without it the Ricin would not be able to gain access to the cells organelles rendering it useless. Once the A chain gains entry into the cytosol its mechanism for attack of the ribosome is depurination of a single endenosine residue in 28S Ribosomal RNA(3) and this inhibits protein synthesis